U.S. patent application number 10/925477 was filed with the patent office on 2006-03-02 for light emitting diode system packages.
Invention is credited to Vladimir Semenovich Abramov, Inesse Petrovna Poliakova, Alexander Eduardovich Puysha, Nikolay Valantinovich Scherbakov, Alexander Valerievich Shishov.
Application Number | 20060044806 10/925477 |
Document ID | / |
Family ID | 34972672 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060044806 |
Kind Code |
A1 |
Abramov; Vladimir Semenovich ;
et al. |
March 2, 2006 |
Light emitting diode system packages
Abstract
Light emitting diode systems disclosed include semiconductor
diodes arranged in cooperation with electrical contacts, mounting
provisions, and optical couplings; where the optical couplings
include at least a Fresnel lens. A Fresnel lens is further coupled
to additional optical elements such as a concave or `negative` lens
and still further to a reflector operating via principles of total
internal reflection. Both the concave lens and the reflector are
aspherical in preferred versions. A cover element of single piece
plastic may be formed in a molding process whereby all three of
these optical elements, i.e. the Fresnel lens, the negative lens
and the reflector, are formed into the single plastic piece.
Further, the plastic piece may be arranged to also accommodate
auxiliary systems such as alignment indexing and fastening means as
well as interlocking peripheral configurations.
Inventors: |
Abramov; Vladimir Semenovich;
(Moscow, RU) ; Puysha; Alexander Eduardovich;
(Saint-Petersburg, RU) ; Shishov; Alexander
Valerievich; (Moscow, RU) ; Scherbakov; Nikolay
Valantinovich; (Moscow, RU) ; Poliakova; Inesse
Petrovna; (Saint-Petersburg, RU) |
Correspondence
Address: |
Joseph Page
PO Box 757
La Jolla
CA
92038
US
|
Family ID: |
34972672 |
Appl. No.: |
10/925477 |
Filed: |
August 25, 2004 |
Current U.S.
Class: |
362/337 ;
257/E33.073; 362/331; 362/332; 362/335; 362/336 |
Current CPC
Class: |
G02B 19/0071 20130101;
F21V 5/045 20130101; F21Y 2105/10 20160801; G02B 19/0028 20130101;
G02B 19/0061 20130101; F21V 17/06 20130101; H01L 33/58 20130101;
F21V 7/0091 20130101; F21Y 2115/10 20160801; G02B 3/0006 20130101;
F21V 5/007 20130101; G02B 3/08 20130101; F21V 17/005 20130101 |
Class at
Publication: |
362/337 ;
362/331; 362/332; 362/335; 362/336 |
International
Class: |
F21V 5/04 20060101
F21V005/04 |
Claims
1) Light emitting diode packages comprising a cover element of
transparent material having a top surface into which a Fresnel type
lens is formed in a surface relief pattern.
2) Light emitting diode packages of claim 1, said Fresnel lens is
formed in two portions, a first portion lying in a circular area of
a plane section, and a second portion lying in a conic section
concentric with the first portion, the conic section has an axis
normal to the plane of the first portion.
3) Light emitting diode packages of claim 2, said cover further
comprising an under surface with a primary lens formed therein,
said primary lens is a concave lens axially symmetric with said
Fresnel lens.
4) Light emitting diode packages of claim 3, said primary lens is
an aspheric lens.
5) Light emitting diode packages of claim 3, said under surface
further comprises a reflector concentric with said primary
lens.
6) Light emitting diode packages of claim 5, said reflector is a
total internal reflection, TIR, type reflector.
7) Light emitting diode packages of claim 5, said reflector is an
aspheric optical element.
8) Light emitting diode packages of claim 2, said cover element
comprises an under surface which forms a concave primary lens and a
reflector, axially arranged in cooperation with said Fresnel
lens.
9) Light emitting diode packages of claim 8, said primary lens is
defined by an equation of the form: x.sup.2+y.sup.2-Az-Bz.sup.2,
and said reflector is defined by an equation of the form:
x.sup.2+y.sup.2+Cz+Dz.sup.2.
10) Light emitting diode packages of claim 9, where A=6.587 and
B=0.537; and further where C=-5.936 and D=-0.85.
11) Light emitting diode packages of claim 2, said Fresnel lens
being characterized as having a different lensing power in
orthonormal directions.
12) Light emitting diode packages of claim 8, said cover element
further comprises indexing and alignment means well positioned with
respect to a system origin and geometric axis.
13) Light emitting diode packages of claim 8, said cover elements
having a periphery of hexagonal cross section in a plane normal to
the symmetry axis.
14) Light emitting diode packages of claim 2, said cover element
includes a top surface having a plurality of discrete Fresnel
lenses, each Fresnel lens in a repeat unit of hexagonal cross
section.
15) Light emitting diode packages of claim 14, said cover further
comprising indexing and alignment means well positioned with
respect to a system origin and geometric axis.
16) Optical sources comprising: a diode; a substrate; and a cover,
said diode is a semiconductor type light emitting diode affixed to
said substrate, said substrate provides mechanical and electrical
coupling to said diode and mechanical coupling to said cover, and
said cover is affixed to said substrate via said mechanical
coupling, said cover is an optically transparent material having a
top surface operable as an optical lens.
17) Optical sources of claim 16, said top surface having a surface
relief pattern thereon, the surface relief pattern forming a
Fresnel type lens.
18) Optical sources of claim 17, said top surface is formed in two
concentric sections a circular planar section and an annular conic
section.
19) Optical sources of claim 18, said cover element further
comprising an under surface having thereon a concave lens sharing
an axis with said Fresnel lens.
20) Optical sources of claim 18, said cover element further
comprising an under surface having thereon a concave lens and a
reflector each concentric with the other.
21) Optical sources of claim 20, said reflector is TIR type
reflector.
23) Optical sources of claim 21, said reflector is optically
coupled to side facets of a light emitting semiconductor diode.
24) Optical sources of claim 20, either of said concave lens or
reflector is an aspheric optical element.
26) Optical sources of claim 24, said lens surface is defined by
the equation: x.sup.2+y.sup.2-6.587z-0.537z.sup.2 and said
reflectors surface is defined by the equation:
x.sup.2+y.sup.2-5.936z-0.85z.sup.2.
Description
BACKGROUND OF THE INVENTIONS
[0001] 1. Field
[0002] The following invention disclosure is generally concerned
with light emitting diodes and more specifically, mounting and
packaging for light emitting diodes.
[0003] 2. Prior Art
[0004] Light Emitting Diode, LED, packaging arts is extensive well
populated with various useful configurations. Indeed, each
manufacture of specialty LED systems tends to re-design the package
to accommodate the special features most interesting to a
particular application at hand.
[0005] Recognized by some as industry leaders, 'Lumileds Lighting
U.S. LLC. of California, make specialty packages to accommodate
high performance features such as high brightness, specialty
electrical contacts, color control, et cetera. Some of Lumileds LED
system packages include unique lens or `cover` elements. One of
Lumileds' cover elements supports high brightness functionality. In
another version, the cover element provides side extending
electrical contacts for surface mounting assemblies. All
manufactures of LED systems apply variations in packaging
configurations to support particular functionality.
[0006] More particularly, and with reference to the art, one will
note special configurations where LED semiconductors are combined
with optical packages including Fresnel type lenses. U.S. Pat. No.
5,528,057 presents a first interesting instance of such
combination. An exit window includes a lens to condense light from
a source buried within the structure.
[0007] Inventors Hatakoshi et al teach in their U.S. Pat. No.
6,611,003 a special Fresnel zone plate device to concentrate and
focus light produced at a semiconductor to a tiny spot. Thus,
semiconductor output beams are manipulated with these special
lenses to achieve preferred outputs.
[0008] An optics package to form highly collimated light includes a
primary lens, a reflector, and a final output lens working in
conjunction with each other to produce a highly controlled output
beam. This invention is presented as U.S. Pat. No. 6,547,423 by
Marshall et al.
[0009] Krames et al recognize the advantage of collecting side
emitted light in their invention of U.S. Pat. No. 6,570,190. Angled
sides increase side light extraction and couple that light into an
output beam.
[0010] Canadian Martineau presents an LED using a single optical
element with Fresnel optics on the inside surface of an output lens
in U.S. Pat. No. 6,616,299.
[0011] Sasajima et al teach of highly collimated output beams from
multiple point sources; these systems include use of Fresnel type
optical elements. In U.S. Pat. No. 5,241,457, a rear window stop
lamp for motor vehicles is described. These devices include an LED
which emits light into a reflector element. Further, the light is
thereafter reflected into a Fresnel type lens before propagating
into an output beam.
[0012] While the field is widespread and busy, the present
inventions have been devised and stand in contrast to those offered
heretofore by others. While systems and inventions of the art are
designed to achieve particular goals and objectives, some of those
being no less than remarkable, these inventions have limitations
which prevent their use in new ways now possible. Inventions of the
art are not used and cannot be used to realize the advantages and
objectives of these inventions taught herefollowing.
SUMMARY OF THESE INVENTIONS
[0013] Comes now, Abramov, V. S.; Puysha, A. E.; Shishov, A. V.;
Scherbakov, N. V.; and Poliakova, I. P. with inventions of LED
system packages including devices and articles. These systems
include highly specialized cover elements having compound optical
systems with exceptionally high light collection efficiency. Each
element of the multi-element optical arrangement is specified and
arranged with particular attention to the nature of light emission
from a semiconductor die like those used in light emitting diode
configurations. In addition to these highly unique cover elements,
these inventions may further include additional subsystems such as
chromacity shifting media, precision indexing and alignment
schemes, high performance substrate mountings, and electrical lead
traces.
[0014] A first noticeably unique feature includes a complex Fresnel
lens. A single Fresnel lens is arranged about two geometric bodies,
a plane and a conic section. These arrangements promote most
efficient coupling of light from the cover into a particularly
specified beam such as a low divergence beam. In addition, special
asymmetric Fresnel lenses are contemplated for beam shaping
functionality.
[0015] Another important feature of these optical source packages
includes aspheric concave lenses and reflectors. Operated with the
object distance less than the focal length; a semiconductor emitter
lies close to the lens surface on its axis, the lens axis being
colinear with the Fresnel lens symmetry axis. In these special
arrangements, a reflector is typically coupled to the side emitted
light while the lens is strongly coupled to the normally emitted
light.
[0016] Some versions include high precision indexing means which
serve both alignment and mechanical coupling functionality. The
cover additionally incorporates a special periphery for placing a
plurality of similar devices efficiently next to one another which
promotes highest density beams.
OBJECTIVES OF THESE INVENTIONS
[0017] It is a primary object of these inventions to provide new
and useful packaging for light emitting diode systems.
[0018] It is an object of these inventions to provide packaging for
light emitting diode systems to produce a preferred optical
output.
[0019] It is a further object to provide packaging for light
emitting diode systems where said packaging promotes highly
collimated optical beams as output.
[0020] A better understanding can be had with reference to detailed
description of preferred embodiments and with reference to appended
drawings. Embodiments presented are particular ways to realize
these inventions and are not inclusive of all ways possible.
Therefore, there may exist embodiments that do not deviate from the
spirit and scope of this disclosure as set forth by appended
claims, but do not appear here as specific examples. It will be
appreciated that a great plurality of alternative versions are
possible.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0021] These and other features, aspects, and advantages of the
present invention will become better understood with regard to the
following description, appended claims and drawings where:
[0022] FIG. 1 is a cross sectional diagram of package in relation
to a `mounted` diode semiconductor in agreement with principles of
these inventions;
[0023] FIG. 2 is a cross sectional diagram showing a light emitting
semiconductor die and its unique emission pattern;
[0024] FIG. 3 is cross sectional view of a cover element;
[0025] FIG. 4 illustrates some special mathematical relationships
and geometries with respect to lens and reflector systems of these
inventions;
[0026] FIG. 5 a top view diagram illustrating a special surface
relief pattern;
[0027] FIG. 6 is a top view of a version having asymmetric surface
relief patterns for specialized applications demanding asymmetric
output beams;
[0028] FIG. 7 illustrates the narrow beam output of a single LED
device of these inventions;
[0029] FIG. 8 shows a pattern formed by an arrangement of a
plurality of repeat units;
[0030] FIG. 9 illustrates the narrow beam pattern formed from a
plurality of repeat units;
[0031] FIG. 10 further details a tiling scheme which may be used to
pave large areas of arbitrary shape;
[0032] FIG. 11 is a side-view cross section of three repeat units
mounted on a single substrate;
[0033] FIG. 12 shows a multi-element compound system; and
[0034] FIG. 13 is a diagram which shows a group cover element and
its coupling system in cross section.
PREFERRED EMBODIMENTS OF THESE INVENTIONS
[0035] In accordance with each of preferred embodiments of these
inventions, there is provided LED system packages. It will be
appreciated that each of these embodiments described include both
an apparatus and that the apparatus of one preferred embodiment may
be different than the apparatus of another embodiment.
[0036] Generally when one refers to an `LED` it is meant that
electronic support, mounting systems and mechanical support, the
lens or lenses and other assorted packaging features, are included
along with the actual semiconductor--the `diode` in the acronym.
This is because these systems are tightly integrated and sometimes
are formed integrally by a manufacturer. When LED units are
commercially produced and sold, they are generally sold as a
complete system including these necessary subsystems. While one
might purchase bare die, reference to an `LED` is directed to far
more that the diode.
[0037] Standard LED packages of the art are typically build about a
lead frame. A reflecting receiving cup or cavity is formed at the
end of an electrical contact. A semiconductor die is affixed at the
bottom of the reflector via glue or soldering. A wire bond connects
a second pole to a second electrical lead; part of the lead frame.
This assembly is put into a mold where a liquefied polymer resin is
injected and envelopes the diode and contacts, and forms a lens
thereabout. The lens and reflector operate to form a more
concentrated output beam. In commonly available LED systems, it is
possible to couple a majority of the output optical energy into a
beam having a divergence of no less than about 30 degrees.
[0038] However in some applications, for example signaling systems
used in railroads, it is desirable and even necessary to couple the
optical output from the diode into a much tighter or `narrow`
output beam. Indeed, specialty applications may call for an output
beam having just a few degrees of divergence. It is possible to
create a narrow beam by placing a light emitting diode at the focus
of a simple lens, however this solution requires an end user to add
expensive optics to the LED packaged source and is accompanied by
additional problems, such as alignment difficulties. It is
preferred that LED packages be custom made to promote a narrow beam
output. To answer this call, highly specialized and unique LED
systems and packages are presented.
[0039] While LEDs having narrow beam outputs are in very high
demand, other pre-specified beams and beam shapes are also
necessary in some application specific projects. For example,
asymmetric beam patterns may be required where illumination fields
are not circular. Very high aspect ratio `ribbon` beams may be
useful in some systems while multiple spot arrays are useful in
others. For these reasons, it is quite desirable to incorporate
high efficiency optical systems directly within LED packages. This
permits a user the luxury of not having to form an expensive
complex optical system exterior to the LED.
[0040] Packages presented here are characterized as having
exceptionally high optical collection efficiency. Further, they
operate to couple optical energy into a highly collimated beam
having low divergence or specialized particular divergence
properties. These systems may also be arranged whereby they are
highly cooperative in groups of similar devices to form a
specialized light output. Further, the systems described are
arranged in special configurations suitable for mass
production.
[0041] With reference to FIG. 1 where a first preferred embodiment
is set forth in a cross sectional diagram, a single piece, molded
plastic cover 1 has formed therein at least five major components
including: an output lens, a primary lens, a reflector, indexing
and mechanical coupling means, and a non-circularly shaped
periphery. The example illustrated in the drawing includes a
substantially planar region 2 defining a top surface of the cover
into which is formed a special surface relief pattern sometimes and
herein known as a Fresnel lens 3. A curved surface is divided into
a plurality of annular regions as is well known in the optical
sciences for making a lens onto a substantially planar surface. In
another surface, a surface which occupies a conic section 4, a
continuation of the Fresnel ridges 5 or surface relief pattern, is
formed. A primary lens 6 which is preferably a refractive lens of
aspherical shape is provided to receive light propagating from a
semiconductor source and couple that light into the material from
which the cover element is formed. A reflecting optical element 7
with lensing power is formed onto a surface of the cover element as
shown. Light incident upon the reflector is redirected in a upward
direction towards the Fresnel surfaces; i.e. the top surfaces of
the cover element. These three optical elements operate together to
form a powerful and highly efficient optical collection apparatus
tuned specifically to the emission patterns of semiconductor die.
The semiconductor die 8 is mounted and mechanically coupled to a
substrate 9 which in some versions is a simple printed circuit or
`PC` board having electrical traces built into its surfaces. Pins
10 formed integrally with the cover element are arranged to fit
with complementary and precisely located receiving holes in the PC
board to form a secure and well aligned mechanical interlock
between the cover and PC board and thus implicitly with the
semiconductor chip.
[0042] As it is a fundamental objective of these devices to couple
light generated in a slab of semiconductor material into a highly
controlled and well defined beam, it is useful to review the nature
and profile of optical output which emanates from the chip. FIG. 2
illustrates one semiconductor and its optical output with
particular regard to spatial distribution. A semiconductor die 21
is typically a rectilinear crystal having a plurality (generally 6)
of planar surfaces. From these surfaces, light generated in the
crystal exits the semiconductor which is under proper electrical
drive conditions. The light does not emanate from a single point in
a spherical wave as ideal worlds might have, but rather the light
emanates with various intensity in directions more or less
perpendicular to a crystal surface with the higher intensities
being in directions more perpendicular. In some semiconductor
chips, a primary beam 22 is emitted from a large top surface. The
beam is brightest on the vertical axis and has reduced intensities
as the angle from the vertical is increased. An arbitrary measure
such as `half-width-at-half-max` HWHM may be used to specify the
beams extrema, indicated by dotted line and angle 24, or maxima
divergence as 35 degrees. The sides of the semiconductor also emit
light in asymmetrical side beams 23. The upper half of the beam
tends to be brighter than the lower half and may be described by a
higher divergence angle. The top half of the side beam may subtend
an angle 25 of about 16 degrees, and the lower half of the side
beam may subtend an angle 26 of about 12 degrees. Careful review
will suggest that in a certain direction, indicated by dotted line
27, perhaps no light at all will be emitted as it is prevented from
escaping the semiconductor chip geometry by mechanisms such as
total internal reflection.
Cover Elements
[0043] One will appreciate great advantages offered by modern
polymer materials sciences. Cover elements of these inventions are
meant to form part of an optical path and are necessarily
transparent and of complex shape. Polymer materials can be prepared
such that their final form is very clear with only slight defects
and occlusions and accordingly make great optical components.
Further, polymers support advanced molding processes which permit
very complex integrated shapes. In the particular instance, a
single piece polymer `cover element` may actually be comprised of
more than seven individual components. While common polymer lenses
known in conventional LEDs usually have only a front spherical
surface, i.e. the system is operated in an immersion lens
configuration; in contrast, these inventions include a cover
element which requires detailed complex integration of many
cooperating components. Thus, polymer materials serve particularly
well the present inventions in a manner not found previously in
uses of polymers to form optical elements.
[0044] A preferred version of a cover element 31 of these
inventions is shown in FIG. 3 in isolation away from any substrate
and semiconductor. The major components molded integrally as a
single piece include at least: primary lens 33, reflector 34,
periphery, output lens 32, and mechanical couplings 35.
Primary Lens
[0045] The primary lens 33 receives light emitted from several
surfaces of the semiconductor and couples that light from a low
index of refraction free space (or other medium) into the high
index of refraction plastic medium of the cover. The high/low index
interface in combination with the curved shape surface forms the
refraction lens. In best versions, the semiconductor chip is
located quite near the surface of the lens and in any case closer
than the focal point of the lens. Thus in this configuration, the
lens is said to be a `negative` lens. While it is possible to
deploy convex lens configurations as a primary lens in these
inventions, it has been determined that the concave configurations
as shown better couple light in a preferred way.
[0046] While some special case versions might include spherically
shaped surfaces, preferred versions include a lens having an
aspheric surface shape. Since this lens is formed in a molding
process and is not ground as glass lenses are, it is relatively
easy to enjoy the benefits aspheric optics offers. A mold tool is
prepared with an aspheric shape and that shape is thereafter
repeatedly passed to cover elements formed in the tool.
[0047] By careful calculation and tedious experimentation, it has
been determined that optical beams emitted from semiconductors as
shown may be best collected and refracted at lenses having aspheric
surfaces described by the equation: x.sup.2+y.sup.2-Az-Bz.sup.2=0.
Still further, the constants of proportionality when defined as
A=6.587 and B=0.537, provide a preferred collection
characteristic.
[0048] The primary lens is axially symmetric and concentric with a
system axis 36.
Reflector
[0049] Reflectors 34 of these systems are special. These reflectors
are preferably aspheric and take the shape described by the
polynomial: x.sup.2+y.sup.2+Cz+Dz.sup.2=0. When C=-5.936 and
D=-0.85, and these reflectors are used with semiconductors of
predetermined form, the reflector performs a beam redirection which
tends to most effectively further couple side beams into the system
output. (Of course, the special case where C=0 renders the
reflector spheric and is considered an exceptional included
case)
[0050] While preferred versions of these reflectors are embodied as
total internal reflection TIR mirrors, that is, a mirror formed at
a high/low index of refraction junction and high angles of
incidence, these are not the only configurations possible. Where
TIR mirrors are not practical, it is possible to polish the surface
and apply a metallic coating to form a reflective mirror. In either
case, the means of reflection is less important than the shape of
the reflecting surface which may in either case be formed in a
molding process.
[0051] The reflector is also axially symmetric, and concentric with
the primary lens. Further, its inside peripheral limit may
correspond with the primarily lens outside periphery at a single
circle.
[0052] One can more fully appreciate the relationship between the
primary lens and reflector in preferred arrangements in view of
FIG. 4 which shows two related parabolas. Plane 41 corresponds to a
plane in which the bottom of the semiconductor is affixed and
bonded. The solid curve 42 is the aspheric reflector which lies in
a first parabola, the solid curve 43 is the aspheric lens which
lies in a second parabolic curve. The space 44 accommodates a light
emitting semiconductor therein. Dotted lines 45 and 46 illustrate
the mathematical constructs which describe the preferred
aspherics.
Output Lens
[0053] An output lens finally couples refracted and reflected beams
into a final condensed output beam and transmits light propagating
in the cover element into free space. Output lenses of these
devices are disposed upon the top surfaces of these cover elements.
By `top surfaces` it is explicitly pointed out that the top of a
cover element is comprised of at least two surface portions. Best
arrangements include a first surface portion of circular area in a
planar section and a second surface portion of annular area in a
conic section. These two geometric bodies are made concentric and
the outside diameter of the circle is identical to the inside
diameter of the annulus. In this way, a very special geometric
advantage is found to support a high performance lens with
particular nature for coupling output of a semiconductor into a
prescribed beam of precise dimension.
[0054] In best versions, surface relief patterns are molded into
the top surfaces during manufacture. Since molding supports complex
shapes, preferred arrangements include high efficiency Fresnel type
lenses. Into a plurality of annular regions, a lens portion, i.e. a
curved surface, is formed. The curved surface of each region
cooperates with the curved surface of the other regions in that the
nature of the curve for all regions is set by a mathematical
relationship having radial dependence.
[0055] In FIG. 5, the top surfaces of a cover element are
illustrated from a top down view. Most importantly, a six sided
polygon or hexagon 51 forms the peripheral limits of the favored
shapes for these devices. A circular demarcation 52 divides the
first top surface portion from the second top surface portion.
Ridges 53 in the first top surface portion form complete concentric
circles. The second top surface portion, that is the surface
portion which lies substantially in a conic section area, includes
similar circular ridges. However, to fit the maximal number of
ridges for best efficiency, some of those ridges are broken about
the circle in which they lie. The annulus marked as 55 is partly
cut off by the peripheral edge of the cover element. Similarly,
most portions of annulus marked as 56 are cut off by the device
periphery. Despite these interruptions, the annular regions remain
in agreement with the mathematical definition for the Fresnel lens
and their surfaces are shaped accordingly. In this way, they
contribute to the total light output and promote a most efficient
narrow beam.
Aspheric Fresnel
[0056] While some preferred Fresnel lenses have simple r.sup.2
radial lens relationships, that is the relationships of spherical
optics, it is also possible to form Fresnel lenses with
aspherically defined surface shapes. The dependence may be
different than simple r.sup.2 and may include a second term
dependant upon the first order radius. Thus the Fresnel lens is
also allowed to a be of non-spherical nature. A highly novel aspect
to this approach includes tuning the curved surfaces in agreement
with the non-spherical wavefront incident upon the lens. More
particularly, tuning the curves of the Fresnel annuli to cooperate
with the particular spatial optical output pattern natural to a
light emitting semiconductor die which is necessarily a
multi-faceted object typically a cube or cylinder having
rectangular cross section.
Elliptical Fresnel
[0057] Further, the lens definition for the Fresnel lens is not
required to be symmetric in the two transverse directions. The lens
may have one curvature in a first direction and a different
curvature in an orthogonal direction. FIG. 6 shows the top of a
cover element of these inventions including a Fresnel lens on its
top surfaces. Further, the figure illustrates two orthogonal
directions R.sub.1 and R.sub.2 indicated by the dashed lines.
Below, are surface topology maps showing the curvature along
direction R.sub.1 is different than the direction corresponding to
R.sub.2. This has the effect of creating an output beam having a
higher divergence in one direction than the other. Thus, an
elliptical beam will be formed as output. In this way, it is
possible to realized beams specified with different divergence in
orthogonal directions; for example a beam of 5.degree. by
10.degree. is created in this way. FIG. 7 illustrates how a single
element LED with appropriately designed cover element 71 forms an
asymmetric output beam having a major axis 72 greater in extent
than the minor axis 73.
Diffractive Alternatives
[0058] Fresnel lenses offer considerable advantage in their ease of
manufacture and high efficiency, alternatives output lenses may be
used in some special versions of these inventions. Diffractive
optics sometimes make excellent high performance beam shaping
elements. Particularly when the output beam is of unusual or
complex shape; for example ribbon beams, multiple spot arrays, et
cetera. Further, diffractive optics such as gratings and kinoform
can be formed in molding processes. Other diffractive optics, for
example holographic optical elements, can be formed in other
processes and applied later to molded covers of these
inventions.
[0059] Periodic gratings formed into the top surfaces of the cover
member of an LED device may be used to efficiently direct the
collected light into a beam of prescribed definition. For example,
a beam characterized by a spot array in the far field may be
achieved via an appropriate grating. Gratings may also be used with
simple outputs. A collimated beam may be supported by a grating
having circular symmetry with increasing period as a function of
distance from the system center i.e. in the radial direction.
[0060] Holograms are sometimes diffractive elements which may be
formed in a medium with spatially varying index of refraction in a
complex `fringe` pattern. These devices may be formed on a thin
film and bonded to the surface of a cover element in a two step
process to form a highly specialized output lens. Holograms could
couple light to any of a great variety of output beams of complex
nature.
[0061] Finally, kinoform micro structures formed onto the top
surface of a cover may operate as an output lens in some versions
of these inventions.
Hex Peripheries in Plurality Systems
[0062] In some applications, it is desirable to maximize the amount
of output light per unit area in an output beam produced by these
inventions. To advance this objective, covers are formed with a
view to arrangements of tightly packed units having minimal losses
there between; i.e. minimal `dead space`. Unit devices can be
formed with hexagonal peripheries which negligibly upset coupling
of light from diode semiconductors into cylindrical output beams,
but permit side-by-side arrangements of a plurality of unitary
devices. FIG. 8 illustrates how cover elements having hexagon 81
shaped peripheries can be tightly packed 82 in a small area.
Despite the hexagonal shape at the device periphery, the beam shape
remains circular and is independent of the shape of the cover
element except in the very near field. Arrangements such as that
shown in FIGS. 8 and 9, have in the far field seven overlapping
beams which form a nearly uniform illumination field. FIG. 9
illustrates this overlap as device ensemble 91 form beam of
circular cross section 92. The illumination field 93 is of good
uniformity due to the integral effect of the plurality of
units.
[0063] Of course, this paradigm can be extended to large areas
where a great plurality of units pave the entire area. FIG. 10
shows how a substantially rectangular surface 101 is covered with a
plurality of units 102. The output beam of this device could remain
with very low divergence; in some cases less than 3 degrees.
Indexing and Alignment Means
[0064] Since these LED packages include high performance optical
elements, i.e. lenses and mirrors, it is part of the entire package
that precise alignment mechanisms be provided. Cover elements of
these inventions are distinct with respect to common cover elements
of most LEDs. Those cover elements are formed with the
semiconductor and lead frame in place while the cover is molded.
Cover elements taught herein are preferably molded and joined with
the semiconductor and base substrate at a later time when the cover
element is hard. As such, opportunity is presented for a highly
precise alignment mechanism.
[0065] A base substrate includes receiving holes therein; said
holes being well positioned and formed with precision. The bottom
of a cover element cooperates with the substrate holes as it has
thereon `pegs` or `pins`. These pins are formed of the same
material (i.e. plastic) as the cover element and they are formed
integrally with the cover element. Where covers are made of
polymers, these pins are ideal as they may be melted over after
they are pushed through the holes of the substrate.
[0066] FIG. 11 shows three units side by each. Each unit 111 is
placed onto the substrate 112 whereby at least two of its pins 113
are pushed through holes in the substrate. When the cover elements
are fully seated in the substrate, a small space 114 is formed
between the cover element and the substrate to accommodate a
semiconductor die therein. The substrate of the figure is shown to
receive three cover elements but is drawn with an undetermined
length 115 which might be extended to great lengths to accommodate
more units.
[0067] It is not necessary that each cover have its own set of
pins. Indeed, it is not necessary that each cover element be formed
individually and contrarily they may be formed as one compound
system. FIG. 12 shows a seven unit cover element formed in a single
mold. Each element 121 shares at least three sides 122 with other
elements and the center element share all of its sides with other
elements. Six pins 123 may be placed in corners as shown to provide
mechanical alignment and coupling means for the compound cover
element which may be brought to a specially prepared substrate with
six similarly positioned holes. FIG. 13 shows how this compound
cover element 131 appears in cross section in conjunction with a
substrate 132. Pins 133 have been pushed through holes in the
substrate so that alignment is assured between the lenses and the
semiconductor emitters mounted on the substrate. In this way, each
unit's top surface 132 operates independent of the others to couple
light into a single beam of low divergence.
Base Substrate
[0068] The base substrate is primarily a mere flat surface. Best
versions include alignment and affixing mechanisms in the form of
holes well placed and precisely drilled through the flat surface
clear through to the other side.
[0069] In some versions, a substrate is fashioned as a circuit
board which includes printed electrical traces for electrical
coupling. Further, the board may include mounting pads suitable for
receiving thereon and bonding thereto a semiconductor die. These
pads should be precisely located with respect to alignment holes in
the substrate for lenses to operate to their full potential. Pads
may be raised to permit an offset between the die and the surface
of the substrate in designs of lenses which prefer such offset. If
a semiconductor die is not well aligned with respect to the lens,
light is not coupled properly into a desired output beam but rather
distortion will greatly reduce the system efficiency. In best
versions, these substrates support wave soldering manufacture
processes. Indeed, A PC board may be processed with many electrical
components, wave soldering, and other associated manufacturing
steps, and thereafter joined with cover elements to form highly
integral LEDs directly on PC boards.
[0070] One will now fully appreciate how high performance LED
packages may be arranged with compound Fresnel type lenses in
conjunction with aspheric optical elements. In particular, LED
packages for producing highly collimated narrow beam optical
outputs or another well defined beam shape of specific nature.
Although the present inventions have been described in considerable
detail with clear and concise language and with reference to
certain preferred versions thereof including best modes anticipated
by the inventors, other versions are possible. Therefore, the
spirit and scope of the invention should not be limited by the
description of the preferred versions contained therein, but rather
by the claims appended hereto
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